The usefulness of digitization of three-dimensional objects is well established. There are known three dimensional digitizing devices which are operative to digitize only the exterior envelope. These include, for example, mechanical arms which follow the exterior face of an object, the coordinates of the tip of the arm being determined by shaft encoders in the joints of the arms. Another example of such digitizing devices employs a stylus which points to a location on the face of an object, while the coordinates of the tip of the stylus are determined by telemetry. A further example of such devices measures the reflection of a beam of energy, such as light, which is reflected off the exterior contours of an object.
A typical mechanical arm digitizer is described in Digital Design, April, 1984, page 104 and is indicated as being available from Micro Control of Vernon CT, U.S.A. under the designation 3D Digitizer.
A typical telemetric digitizer is known as 3-Space and is available from McDonnell Douglas of St. Louis, MO, U.S.A.
Apparatus for conversion of 3-dimensional points measured on a part surface into a CAD model is known as CADDInspector and is stated in the Klein Report, Vol. 10, No. 13, Jul. 13, 1988 as being available from CADKEY of Vernon, CT, U.S.A.
It is also known to generate three dimensional images of relatively soft tissues which are cut with a microtome. This technique does not provide registration of the images and is not suitable for engineering objects.
Computerized tomography and radiological scanners provide slice information for objects but generally are not suitable for use in an industrial environment in terms of their speed, model size capacity, accuracy, resolution and the types of materials on which they can operate.
In an article entitled "Three-dimensional reconstruction from serial sections: iv. The reassembly problem", by Prothero J. S. et al (Computer, & Biomed. Res. (USA), vol. 19, no. 4, pp. 361-373, August, 1986) there is described a reconstruction technique wherein thin slices are cut sequentially from an object. After cutting, the slices are digitized by conventional two-dimensional digitizing techniques.
In an article entitled "Building, visualizing and computing on surfaces of evolution", by H. Harlyn Baker (IEEE Computer Graphics & Applications, July, 1988, pp. 31-41) there is a discussion of reconstruction of three dimensional surfaces of an object from two dimensional slices thereof.
U.S. Pat. Nos. 3,649,108 and 3,884,563 both relate to layer-by-layer photographing of a specimen. After a given layer is photographed, that layer is removed from the specimen and discarded. U.S. Pat. No. 3,884,563 describes at column 2, line 15, the use of a computer scanner. U.S. Pat. No. 3,649,108 describes at column 3, lines 16-20, the use of a filler material which is usually translucent or transparent.
It may be fairly said that the prior art devices described above are not able to provide uniformly high resolution volumetric digitizing of generally all shapes of objects.